Subcritical Water Extraction of Sesquiterpene Lactones from Inula racemose

Inula racemose, a traditional Tibetan medicine with strong antifungal and anti-inflammatory activities, contains large amounts of sesquiterpene lactones. In the current study, subcritical water extraction was employed for the efficient extraction sesquiterpene lactones from I. racemose. Various parameters, such as extraction time (23.2-56.8 min), temperature (129.5-230.5 degrees C) and SW flow rate (1.3-4.7 mL/min) was investigated for optimizing the recovery of the targeted compounds. The optimal conditions for SWE were determined as follows: extraction time of 45 min, extraction temperature of 190 degrees C, and SW flow rate of 3.0 mL/min, and a recovery of 71.97% was achieved. Four sesquiterpene lactone isomers were separated by prep-HPLC from the SWE extract and identified as igalan, isoalantolactone, alantolactone, and alloantolactone. A comparison of SWE with traditional extraction technologies showed that subcritical water could be a green and efficient substitution for the extraction of sesquiterpene lactones from I. racemose.